The ATSB investigation has classified the airspace incident near Launceston on 24 December as a 'serious incident' and has recommended a review of certain aspects of NAS airspace implementation in Class E airspace including education, training and chart frequency material.
Unlike previous reports made to the Australian Transport Safety Bureau since the NAS 2b changes from 27 November, of which two warranted investigation, the ATSB has determined that the occurrence near Launceston on 24 December was a type of serious incident known as an 'airprox'.
The ATSB investigation found that a 737 passenger jet on instrument flight rules (IFR) descent into Launceston had to initiate an immediate climb to avoid a potential collision with a Tobago general aviation aircraft travelling under visual flight rules (VFR) at an altitude of about 7,500 feet in the opposite direction.
The 737 crew did not see the Tobago at any time, even after traffic alert and collision avoidance system (TCAS) traffic advisory (TA) and resolution advisory (RA) alerts.
The Tobago pilot saw the 737 but thought his track would be sufficiently separated from the 737 not to present a risk of collision and therefore took no evasive action.
While the ATSB investigation could not conclusively determine the reason the Tobago passed so close to the left of the 737 when its intended track should have led it to pass to the right, the discrepancy was within the tolerances of the various navigational equipment.
The ATSB investigation was of a single serious occurrence and does not provide the basis for a major change to the US-based NAS, which is yet to be fully implemented in Australia. However, based on the circumstances of this serious incident, the ATSB has recommended that CASA and Airservices Australia, in consultation with the NAS Implementation Group, review NAS procedures and communications requirements for operations in Class E airspace, particularly for Air Transport operations during climb and descent in non-radar airspace, with a view to enhancing pilots' situational awareness.
While the ATSB does not want to be prescriptive about the review, the Bureau believes that it should include examination, and where necessary revision and updating, of education, training and chart frequency material. It is also desirable that the responsible authorities seek industry input in their review.